The invention relates to the field of cosmetic product dispensers in the form of and known as xe2x80x9csticksxe2x80x9d, the cosmetic products thus dispensed being typically of the pasty type and most often deodorants.
Known dispensers include most often:
a body forming a skirt or a side wall containing a cosmetic product propellant device, and open at two ends, the cosmetic product having to rise to the surface at an upper end in order to be applied,
a cover or a cap closing, typically in a sealing way, the upper end,
a bottom, either fixed to the body, or integral with the propellant device,
a propellant device typically includes two parts mobile one relative to the other, one being constituted by a plunger in the form of a nut adjusted to the shape of the body, the plunger, which bears the cosmetic product, being typically moveable axially but not in rotation, either due to the non cylindrical shape of the body, or, if the body is cylindrical, by engagement of at least one axial rib carried on the inner surface of the body and of at least one groove formed on the periphery of the plunger, the other including typically the following components, possibly in the form of a part cast in a single piece:
a base plate fixed to the body as far as axial movement is concerned, but free in rotation, the fixing to the body being made typically by clipping or snapping on,
a threaded screw, integral with the base plate, carrying and engaging with the plunger forming a nut,
a screw drive knob, which may possibly be constituted by the bottom itself, allowing the user to move the stick form cosmetic product axially, and therefore to bring it up to the upper orifice of the body, as it is consumed.
In a known way, the plunger and the base plate have apertures which allow the dispenser to be filled through the bottom, the dispenser being closed by its sealed cover.
Also in a known way, the dispenser is formed by assembly, particularly by snapping on or by clipping, of the propellant device in the body, the other parts of the dispenser being also generally assembled in this way, reversibly as regards the cover, and irreversibly as regards the bottom or the knob activating said screw.
Thus, as examples of patents describing dispensers may be cited French patent no. 2 573 734 or again European patent no. 462 925.
Problems Posed
As already indicated, known dispensers include a plunger forming the cosmetic product stick medium, which is forced into an axial movement as soon as the user rotates the screw, by subjecting the bottom or a knob provided for this purpose to a rotation relative to the dispenser body.
Sometimes dispensers carry an indication, by means for example of a printed arrow, of the so-called xe2x80x9cpositivexe2x80x9d direction in which it is appropriate to rotate the bottom or the knob so as to bring the plunger up.
But most often, dispensers carry no such indication, an indication of this kind, although practical in nature, being of no particular help in giving the dispenser a xe2x80x9ctop of the rangexe2x80x9d product image or in improving its appearance.
Furthermore, even if dispensers were to carry this indication of the xe2x80x9cpositivexe2x80x9d rotation direction, this indication would not necessarily be observed, given the variety of situations in everyday life, since these dispensers can fall into the hands of children who play with any object which comes to hand, or adults who pay little attention to the indications carried by the packaging, or else people tempted to go against what is indicated, just to xe2x80x9csee what might happenxe2x80x9d etc.
In all these circumstances, there is a risk of seeing a rotation forced on said screw, while the plunger-nut is locked, in the down position after rotation in the xe2x80x9cnegativexe2x80x9d direction, which will irreversibly damage the xe2x80x9cscrew-nutxe2x80x9d unit.
A solution to this problem is already known from U.S. Pat. No. 5,733,058 in the case of a top filling dispenser. This dispenser includes particularly a partially threaded central screw (denoted by the reference 14) and a stick medium (denoted by the reference 16) which includes a trough integral with a threaded nut engaging with said screw, said threaded nut being of a flexible material able to distort under stress in the event of locking of said trough relative to said screw.
However, on the one hand, this patent does not bring a solution in the case of current bottom filling dispensers, on the other hand, if this patent does disclose an idea, it does not necessarily teach how to form a nut which would be xe2x80x9chardxe2x80x9d enough to fulfil its xe2x80x9cnormalxe2x80x9d function which is to make the stick move up or down, and which would be xe2x80x9csupplexe2x80x9d or xe2x80x9csoftxe2x80x9d enough to fulfil its xe2x80x9coccasionalxe2x80x9d function which is to distort when the central screw is rotated in the wrong direction and when the stick medium is at a stop. There is no evidence that a satisfactory compromise exists of a nut able to fulfil these two functions even in the case of a top filling dispenser.
Additionally, using a xe2x80x9csoftxe2x80x9d material for the nut presents the obvious risk of causing damage to the inner thread of the nut.
Lastly, in the case of bottom filling dispensers, the stick medium, which is typically a part cast in a single piece, must furthermore be a fairly rigid part, which is not compatible with the material flexibility required by the solution described in U.S. Pat. No. 5,733,058.
Means intended to resolve a similar problem are furthermore known in other types of packaging, lipstick tubes in French patent No. 1.519.560, a mascara tube in Japanese patent No. 08 154736, but they are not adapted to the case of a dispenser according to the present invention.
The purpose of the invention is therefore to find a solution to the problem posed which may be used in a bottom loader dispenser, which is technically reliable, and which, in terms of mass production, gives sufficient latitude to obtain consistent production quality.
Incidentally, the purpose of the invention is to provide an audio means of alerting the user and of inviting him to change the direction of rotation of the drive knob or of the bottom as the case may be.
The object of the invention is a dispenser which resolves the problems posed, in such a way that the user cannot destroy the engagement between the screw and the plunger, an engagement of the xe2x80x9cscrew-nutxe2x80x9d type, however the dispenser is handled.
According to the invention, the typically cosmetic product dispenser in stick form includes a body, a cap, a propellant device including a base plate fixed to said body, and an axial, spiral or so-called xe2x80x9cmalexe2x80x9d helical threaded screw, fixed on said base plate, a plunger formed of a medium of said stick and of a central, spiral or so-called xe2x80x9cfemalexe2x80x9d threaded nut, engaging by screwing with said axial screw, a bottom and/or a knob for rotating said screw, said medium and said body possibly including axial guide means, typically by engagement of at least one axial rib on the inner surface of said body with at least one axial groove on the periphery of said medium, so as to provide, in the case of a cylindrical dispenser, axial movement of said stick by rotation of said knob or of said bottom, and is characterised in that:
a) engagement between the so-called xe2x80x9cmalexe2x80x9d helical thread and the so-called xe2x80x9cfemalexe2x80x9d thread is partial, one of the two threads extending only over a predetermined angular fraction, so as to form a so-called partial thread,
b) said central nut and/or said axial screw include a radial resilience means, constituting an aptitude for radial distortion under stress, so as to allow, in the event of forced rotation under said stress and of locking of said screw relative to said nut, a disengagement, i.e. a relative axial movement of the xe2x80x9cmalexe2x80x9d and xe2x80x9cfemalexe2x80x9d spirals, by overlap of the spirals and clearance of a screw thread, without destroying said engagement between screw and nut,
c) said base plate (4) and said medium (8) of said stick are open-worked so as to allow said dispenser to be filled through the bottom,
d) said medium (8) includes radial platelets (80) fixed to said central nut (7) which has, in the sectors between said radial platelets (80), a thinned down wall (72).
In this way, the applicant company has been able to observe that, thanks to this combination of means, it was possible to fix at a pre-determined level a disengagement torque value between screw and nut, i.e. the value of the torque which leads, following a locking of the rotation between screw and nut being lockedxe2x80x94particularly when the nut reaches the bottom end of the screw integral with the base plate, to the spirals overlapping and to their being axially offset. It is important to have this possibility of varying this level since it must be positioned between two thresholds:
on the one hand, a lower so-called use threshold, corresponding to the xe2x80x9cstandardxe2x80x9d torque under xe2x80x9cnormalxe2x80x9d conditions of use of the dispenser, which may vary according to the packaged cosmetic product,
and on the other hand, an upper so-called break threshold corresponding to a torque causing damage to the dispenser or to the screwing threads of the screw-nut unit, a threshold which will vary particularly with the mechanical characteristics and/or the thickness of the materials used to form the dispenser.
Thus, with the invention, the user will never be able to apply to the dispenser a torque equal to the break torque, since well before this threshold is reached, an overlap of spirals will have occurredxe2x80x94without destruction of the spiralsxe2x80x94in respect of a pre-determined torque value, thanks to the means of the inventionxe2x80x94this is what is termed xe2x80x9cdisengagementxe2x80x9d between screw and nut.
Generally speaking, a new 360xc2x0 rotation produces an overlap of one spiral, with the result that the user is able to realise that the direction of rotation should be reversed. The invention therefore brings total safety to the use of dispensers, even if they fall into inexpert hands which might inadvertently apply to the dispenser far too high a torque.